Medicine: Malaria in Manhattan

A Bowery bum died of malaria in Manhattan. He must have just come from the tropics, reasoned Chief
Medical Examiner Charles Norris, and casually noted that the derelict
had been a narcotic addict. Another Bowery bum died of malaria, and
another, and another. Dr. Norris called his assistants together,
ordered: "There's a carrier loose down around Park Row. Watch for him."

"He's a dope," added Dr. Milton Helpern, one of Dr. Norris'
assistants. Perspicacious Dr. Helpern had noticed that every dead
malarial bum had been a drug addict. He visualized a huddle of men...